Cell reprogramming advances

Simple 'STAP' method based on exposure to stress, mild acid

KOBE – A team of scientists led by a woman from Chiba has discovered that by simply exposing body cells to acidic liquids, the cells can be reprogrammed to grow into any type of mature tissue.

The discovery was announced Wednesday in the journal Nature.

The method, which differs from the one developed by Nobel Prize-winning scientist Shinya Yamanaka to create induced pluripotent stem cells, or iPS cells, could have a far-reaching impact on cancer research, regenerative medicine and new drugs.

The research was conducted by scientists at the government-backed Riken institute and Harvard University and led by 30-year-old Haruko Obokata. A scientist at Riken’s Center for Developmental Biology in Kobe, she also spent time doing research at Harvard.

In experiments, the scientists soaked lymph corpuscle taken from 7-day-old mice in mildly acidic liquids for about 30 minutes. A few cells that survived were cultured and transplanted into mice, where they developed into nerve and muscle tissues.

Under normal circumstances, cells that have matured into specific cells can’t be reprogrammed. But the researchers discovered a new way of reprogramming adult cells. They named the method of generating pluripotent cells, or cells that can grow into any type of mature tissues in the body, “stimulus-triggered acquisition of pluripotency,” or STAP.

Obokata told reporters that the method “may lead to the regeneration of organs and tissues in the body and the development of new medical technology, such as one aimed at suppressing cancer that would be caused by stress on cells.”

The scientists say STAP cells can also become tissue that forms the placenta, something not possible with iPS cells that are created by injecting four gene control agents into an adult cell, or embryonic stem cells.

STAP cells can be produced within a shorter period of time than iPS cells, which can take several weeks to produce. The risk of STAP cells developing cancer in the body is also believed to be lower than that of iPS cells.

Success rates to make STAP cells ranged between 7 and 9 percent, higher than those for iPS cells.

STAP cells can be made from skin and muscle cells, not only from blood cells.

As well as immersion into a mildly acidic solution, such stresses as the passage of cells through glass tubes and exposure to a mildly toxic substance were found to be effective for their production.

The team believes that external stimuli help change how some genes in the cells work, although it is uncertain how such a change occurs.

Obokata and her colleagues confirmed STAP cells’ ability to develop into any tissue, as mice that received STAP cell-injected embryos gave birth to chimera babies.

They also found the premature cells can contribute to the formation of the placenta in the experiment.

Furthermore, the team successfully converted STAP cells into highly proliferative stem cells, though the stem cells were found to have lost ability to develop into placental tissues.

Researchers have been surprised by the discovery.

“I am proud that such important research results have been released by Japanese researchers. I hope that pluripotent cells will be made from human cells under the same method,” iPS cell inventor Yamanaka said.

“This is amazing,” said Arata Honda, an associate professor at the University of Miyazaki, who was briefed on the research. “High-quality cells that could exceed the existing pluripotent stem cells have been created in an enormously simple way.” But much remains unknown about STAP cells, including why they can only be cultured but not created inside the body, and why such cells are created at all. Observers say it will take further research to see if the same thing can be done with human cells.

Obokata and her team are studying whether STAP cells can be produced with human cells and those of other animals.